Method for aiding audition



July 24, 1928; 1,678,564

B. E. ELDRED METHOD FOR AIDING AUDITION Filed Dec. 10, 1924 l l dl eGexjezwfbr v II .2 z

MM: Earner-afar l Patented July 24, 1928 UNITE-D -sT'ATE IS 'IHPAT-YEINTOFFICE.

BYRON ELDRED, or msme'ron, mew Yonx.

METHOD FOR AIDING AUDITION.

Application as December 10,1924. Serial no 755,077.

My invention consists in 'a' method and apparatus for aiding theaudition of persons of defective hearing.

The method consists in producing and.

emitting into the surrounding space a continuous and sustainedsuccession of rythmical air Waves of suiiicient pitch and-amplitudewhereby the ears of persons, of defective hearing are rendered moresensitive to normal sounds. S uch waves are hereinafter referred toassensitizing waves.

y method is useful not only in enabling more or less deaf persons tointelligibly hear sounds or speech of normal intensity while, they arewithin the influence oi such waves,

but also for improving the audition of somev repeated'subjecclasses ofdeaf persons, b tion to the influence such sensitizing waves. w While llfind that in most cases of defective audition the. sensitizing. wave-maybe applied to the best advanta e at a certa n pitch and amplitudeto suitt e special case of deafness, and this pitch and amplitude may bereadilydeterinihed by experiment for an individual case, i also findthat greatly improved hearing results in most cases by waves ofinaudible frequencies and substantial magnitude. Such waves 'I proposefor general use in theatres, churches, auditoriums, homes and the like,.tinditwill be obvious tea-person skilled in the art that the amplitudeof the wave so employed should he adjusted to suit the dimensions andgeneral interior design of the auditorium.

In improving the acoustic properties of auditoriums, theatres, churchesandthe like for the reception of sound by persons of dc fective hearing,I find that sensitizing waves in irequenc' and amplitude predeterminedfor a suitab e sensitizing effect. for average persons of defectivehearing are effective. These waves have a healthy natural efiect uponthe abnormalear which is probablybrouight about by efiectingaresponsiveness o the tensor tympani muscle; 'lhis tensing efiect uponthe relaxed vibratory system of the deal ear is practically entirelywithout efiect upon the normal healthy ear. I do not, however, wish tolimit myself to the use of inaudible frequencies in the car-- rying outof my invention as certain audilole frequencies, especially thoseapproaching the limits of audibility, will he found to be quitesatisfactory-hut waves of low roughly placed between and 5000 doublevibrations per second, although the authorities diflt'er widely astothese limits.

I find that it is desirable to use a wave which has little or notonalquality for the or no auditory nerve response and for that reasonmay be ap lied with the desired strength or amplitu e without causingnerve humanear because such a wave efiects little fatigue, or cardiscomfort, especially to per-- 1 sons of normal hearing.

In thepractice of my invention, the adustment of amplitude is apparentlymore important than the adjustment of frequenciesxof vibration. I findthat too great an amplitude may operate to defeat the purposes of theinvention and that deaf persons within the influence of sensitizingwaves of too great amplitude may not hear, and may experienceuncomfortable sensations.

. In soine special cases, particularly in, chiltions of'highfrequency.

In, either case, the essential condition is that there is produced aforceful action by the air waves on the mechanism of the ear. WVithwavesot low frequency, the amplitude of the waves isv made sufiicient toadequately afl'ect the ear mechanism, while with waves of high frequencythe effect of the very rapdren, it will'be found necessary to use vibra-4 idly repeated applicationof the smaller am pliti1de waves exerts suchforce on the ear mechanism as to produce the desired eiiect. Thereis nopractical diiiicnlty in properly adjusting the amplitude of the waves,since thewave-producing mechanism may be adjusted to the proper degree,or the listener may vary his distance from the wave-producing apparatus.

It is well known that deaf people who can he made to hear at allrequire-sound waves of excessive amplitude (i. every loud tildtalking)to overcome their defective audition.- I have found that sensitizingwaves oi sub-audible or super-audible frequencies serve the same purposeas supplying exces-' sive amplitude. to the sound waves of thesoundcommunication to be imparted. And the-relief efiected by myinvention is thus two-fold in that in voice communication it saves theefi'ort of very'loudtalking by the person who is endeavoring tocommunicate with the person of defectiveaudition.

The sensitizing waves used in thisman ner while referably of pure form,need not be so free rom what may be termed staccato components. nor ofas great am litude as when amore lasting efiect on the caring is to bereduced- In this latter'j case the waves s ould. be of substantiallypure form, that is containing a dominant percentage of afundamental notenot compounded with waves of difierent frequencies. a

I do not wish to be limited. to any special" type of apparatus or devicefor carrying out my invention. I have shown and describeddiagrammatically two types .of apparatus which I have found suitable:Fig. 1' shows an apparatus for the generation of low frequencysensitizing'wav'es; Fig. 2 shows an apparatus forthe generation of highfrequenc sensitizin waves Re erring to Fig. 1 M is a motor having arheostat. R in its field circuit to control the speed of the motor. 'Nis a self-excited alternatin current generator having a commutator 1from;which direct current is delivered to the field magnet coils N andthrough wires 20, 21 to the coil L surround ing one limb T of the magnetI. Collector rings N, on, the generator shaft deliver alternatingcurrent through wires 22, 23, to coil L this circuit including a,resistance R The coil L consists of onl a few turns, is light in weightand woun around'the tubular end of a cone shaped diaphragm D of lightfibrous material, such as paper or archment, which is carried by a thinrub- .er ring F secured to the edge of a circular opening in the bafileplate B. The diaphragm is thus free to move in the direction of itsaxis. The coil L is located in the magnetic field between the poles 1,,I of the magnet I, the end of the core I, extending into the coil L Dueto theoscillations of I the alternatin current, a magnetic field willtion wit be set u in 3 which will change its direceach change indirection of the oscillating current. When this magnetic field is in thesame direction as that due to magnetl, the two fields will act to attract each other, thereby causing coil L to .move along its axis from;its normal position-. When the magnetic field of L reverses itsdirection a repelling action will take place and the coil L will move inthe other direction. In this manner the diavrected. The frequency of thewaves may be controlled by rheostat R andthe amplitude may be varied byrheostat R For producing high frequency air waves, I may use the deviceshown in Fig. 2.. The

wave generator is of the same construction as that 'desc'ribedin Fig. 1,the unidirectional and oscillating currents delivered to the coils. Land iL, being furnished however from an alternating current rectifier"and an oscillator of the vacuum tube audion ty Referring to Fig.2,24an'd 25 are the usual 35 alternating current supply mains and areconnected to the primary coil T, of a transformer which has three othercoils on the same ironcore T. vCoil T has many more turns than theprimary and operates as a step-up transformer generating a high voltaged1fi'erence at its terminals. Each terminal is connected to the anode orplate of thermionic rectifiers R, and R which permit current to flow inone direction only, viz, from plate to filament. Current to heat thefilaments of the rectifier tubes is furnished from a third coil T woundwith a sufficient number of turns to produce an induced voltageof'proper amount. The cenconnecting the center point of the coil anearly constant voltage is available which is practically equal to halfthe voltage at the terminals'of coil T. It is this constant voltage thatoperates the oscillator to be later described. The coil T supplies cur--rent 'for the filament of the three-element vacuum tube 0-.

The oscillator unit is the A enerator' of high frequency currents whicconverted into sound waves at the pitch andamplitude required for thepurpose of the invention. The operation is exactl the same as-that ofany "vacuum" tube an ion oscillator and'consistsin supplying the three-195 element vacuum tube 0 with a high voltage to its anode through thecoil L A magnetic field will be set up in this coil due. to the anodecurrent and will react in coil L to induce a voltage in it. This voltagewill are later he impressed upon the grid of the vacuum tube and, as thepotential of the grid controls the assage of current in the anodecirother terminals connect to the cuit, it Wlll be apparent that steadyoscillations will be generated in the coils L and L and condensers C--1to C-7,'the perlodicity of these oscillations depending upon the valuesof these parts. In order to isolate the grid "from. the high voltage ofthe anode circuit the condenser C-8 is provided. The capacity of this,condenser is-very large and therefore its reactance to the oscillatincurrent. is very low at high frequencies, hut-it has infinite reactanceto the dlrect current of the anode circuit. Switches, are provided toconnect in the proper condensers for any potential of coil T 'These conensers operate in conjunctionwith L,-to. suppress any" undesirableirregularities .in the anode. cur

rent from the alternating current converter and thereby cause othervibrations than those desired to be heard when the set 1s 1n operation.

When the switch S is closedthe alternating current in coil 'I sets upavarying magnetic field in the core T. and the secondaries will eachhave induced in them voltages depending uponthe number of turns.Alternating current from coil T .will pass through the rectifiers R andR 'The filaments will be heated by a current fiOWlIlg from T Theoscillator filamentis heate from coil T The rectified alternating cur-'rent willthen flow from the center of coil Kid oscillating current. 5%

tilt

(lid

' mined fundaimental.

are a series of condensatlo'ns and rarefac- T, through L, therebyenergizing magnet I and thence through oscillator O01l L to the vacuumtube 0 and back to- '1 through the common connector'between coils T, andT Theoscillations in L L and L and the condensers C-l to 0-7 are thusestablished. Due to these oscillations a magnetic field will be set up.in L, which will change'lts direction with each change in direction ofthe The diaphragm D will therefore oscillated in the manner previouslydescribed to produce air waves oi any required high frequency'. I

Each of these devices Wlll produce rhyth-a mical waves which produce theeffect of sinusoidal waves in that they contain a suf of the" predeterficiently large percents ound waves in air tionsor variations inpressure, and these audition through extended treatment.

int of'zero variations inpressure operate upon the ear drum and itsaccompanyin mechanism to cause the sensation of soun The arrangementshown in Figs. 1 and 2 may beused either for the correction of defectiveaudition while the person is within the influence of the sensitizingwave or for therapeutic application to correct defective the first purose relatively low energy,"such as of the or er of five or ten watts, sused,

while'for the second purpose much higher powers, as for exampletwo tothree hundred watts. may be needed.

It is quite 'racticable to employ vacuum "tube circuits tor thegeneration or low fre- .quency oscillations, but the apparatus is morecomplicated and cumbersome due to For.

the necessity of using large values of inductance andcapacity. v

.I-believe I am the first to propose the correction of defectiveaudition by means 'of a device which conditions a deaf ear to respond tosounds which are heard by the normal ear and not otherwise heardintelligibly by the defective car. My invention concerns conditioningthe defective ear for hearing by pervading a region in which the'heareris located with practically unnoticeable waves of predeterminedfrequency, and amplitude, which I have. proven to be efiective or thispurpose. All other means disclosed in the art employ devices forconditioning the sound waves for reception by the defective ear eitherthrough volume collection or amplification'of the original sound. 7Accordin'gto my invention, instead of magnifyingthe sounds to be heard,I-improve the sensitlveness of the receiver, that 13 to say, thereceiving ear mechanism. In practice of my invention, by means-of asuita-blede-,

vice I cause to be freelye'mitted into space about the personofdefective hearing the sensitizing waves. The volume of s acesensitized for correcting audition wil or course depend somewhat uponthe size of the diaphragm or other suitable device employed to produceair waves, likewise the amplitude of the wave as generated will affectthe d-istance'of its useful employment. I find howeverthat the wavesgenerated by the apparatus I have described herein are 'efiectlve over avery considerable area. A

' diaphragm of twelve inches or less will sen-.

sitize 'under proper conditions of application, the largest auditorium,and a. six inchdiaphragm has served satisfactorily at a distance ofthirty feet out of doors.

It is well known that many persons of defective hearin can hear loudsounds. Based upon this fact various devices have been constructed toaid audition, comprising in principle sound collecting devices such asear trumpets and sound amplifying devices on the principle of thetelephone transmitter noise conditions, for example some persons ofdefective hearing unable. to hear normal time speech under ordinaryconditions, can.

While riding on a railroad train hear ap parently better than persons ofnormal aud1- tion' under like conditions.

'Under such circumstances thedeaf erson hears because the amplitude ofthe noise vibrations is greater than that of the'normal or ordinaryvoice vibrations which the deaf person can not hear. Similarly,according to my invention, the amplitude of the substantiallyIlOiSGlQSSl/lbl'ilhlOIlS produced is greater than those which "wouldoccur in normally audible sounds, I and accordingly theear mechanism ofthe person hard of hearing is subjected to pressure variations greaterthan those occurring in normally audible sounds. l have established thefact that the necessary condition to make deaf ears responsive isamplitude of air Wave vibration, and that it is not'necessary toaccomplish this with a wave which creates a noise or even an audiblesound. 7

While I have described particular forms of apparatus which have beendeveloped by long experiment and have been found to be suitable for thepurposes of my invention,

aeratorit is to he understood that other forms of apparatus whichoperate in a similar Way to produce similar results are Within the scopeof my invention.

As a continuation in part of this application I have filed applicationSer. No. 204,148, July 7, 1927,

ll claim: p

1. A method or improving the acoustics or audihility qualities of apredetermined space for persons of dificult hearing therein, whichmethod consists'in maintaining in the atmosphere of said space acontinuous succession of rhythmical air Waves of such amplitude as tocause pressure variations greater thanrthose occurring in normalunamplified sounds, the said-Waves having a frequency adjacent themarginal frequency of the audible range.

2. A method oiimproving the acoustics or audihility qualitiesof apredetermined space for persons of defective hearing therein whichmethod consists in maintaining in the atmosphere of said space acontinuous and sustained succession of airwaves 011 such force'producingcharacteristics as to cause pressure variations greater. than thoseoccurring in normally audible sounds, the said waves being of suchfrequency as to be substantially inaudible.

In testimony whereof, l affix my signature.

